In a follow-up of slightly more than five years, 324 patients had a recurrence of cancer, 223 died with a recurrence, and 28 died without documented recurrences.

The more closely patients followed the high-fat Western diet, the more likely they were to have a recurrence. Compared with the one-fifth whose dietary pattern s least resembled the high-fat diet, the one-fifth whose patterns most resembled it were 3.25 times as likely to have a recurrence of cancer or die. Western dietary patterns, the scientists write, are associated with higher blood levels of insulin, and insulin is associated with enhanced tumor growth.

Dr. Charles S. Fuchs, the senior author and an associate professor at the Dana-Farber Cancer Institute in Boston, said he did not advise a radical diet for patients. ''I don't tell them they can't ever eat meat,'' he said. ''Once or twice a month is not a bad thing. It's the people who are at the extremes that are in trouble.''

The researchers, whose study appears in the Aug. 15 issue of The Journal of the American Medical Association, acknowledge that this was an observational study that did not prove causality.